Gantries, including multiple axis gantries, are generally known in the art. Multiple axis gantries are used to position work devices attached to a work piece carriage of the gantry. The gantries include tracks or guides along which the work piece carriage moves by means of electric motors or other input devices along the various axes to most accurately position the working device. Gantries have been used for moving items from one location to another including gantry cranes for lifting containers off of barges, moving work pieces throughout factories, and selecting individual components from predetermined locations as well as in devices operating while in continuous motion CNC machines, pen plotters, laser cutters and the like.
To position the work piece carriage, one type of multiple axis gantry, for lighter duty applications, includes linear actuators incorporating lead screws or ball screws driven by electric motors such as the Macron Dual Rail X-Y System commercially available from Macron Dynamics, Inc. of Horsham, Pa. Typically, a first linear actuator moves a second linear actuator mounted in transverse relation to a movable carriage of the first linear actuator. The second linear actuator includes and positions a second carriage that functions as the work piece carriage. With the second linear actuator aligned transverse to the first linear actuator, the gantry provides two axes of travel along which the work piece carriage may be positioned. Unfortunately, if the work piece carriage is moved to an end of the second linear actuator, offset loading can occur and create large torques on the first linear actuator requiring the structure of the first and second linear actuators to be extremely strong and rigid, which can make the gantry large and bulky, costly as well as difficult to manufacture in custom sizes. To rectify the problem associated with offset loading, other types of multiple axis gantries include a pair of linear actuators positioned proximate the ends of second linear actuator to prevent the previously discussed offset loading and resulting torques.
Alternative linear actuators incorporate belt driven carriages such as the ELZU MODULAR Linear Actuator commercially available from Nook Industries of Cleveland, Ohio. The linear actuators incorporate endless belts driven by drive motors that actuate the work piece carriage or the other linear actuators. Unfortunately, the use of belt driven linear actuators can further the difficulty and cost of manufacturing custom sized multiple axis gantries. Custom size gantries require custom length drive belts, and manufacture of infinite sizes of belts can be very costly and impractical.
There exists, therefore, a need in the art for a multiple axis gantry that is configured and manufactured such that it can be easily and inexpensively manufactured as well as easily and cost effectively manufactured in custom sizes.